But at other times and in other places, the taboo has been exceptionally strong, as Young points out: In the tenth and eleventh centuries in Europe, marriage was prohibited by canon law between anything up to sixth cousins; in other words, as far as, and perhaps sometimes farther than, the family records could reach.
It was only in 1918 that Roman Catholic canon law got around to allowing third cousins to marry, and it still does not allow first cousins to do so. It has always been easy to get dispensation from these provisions, but they were, and are there.
The penalty for incest has been death at various times and places, and is still prison, though in most civilized countries now, the forces of law and order are as quick to send an offender to a psychiatrist as to exact the full rigor.
Brother-sister incest was, oddly enough, not a criminal offense in England between 1660 and 1908, but was only an offense at the Canon Law.
Thus it can be seen that the taboo against incest has been a changing thing, the seriousness of the offense and the severity of the punishment being subject to the whims of those who at a given moment in history are charged with enforcement of the moral code.
While acceptance of sexual intercourse between a father and his daughter is most likely beyond what our society is capable of writing into its moral code at any time in the foreseeable future, it is certain that we are now in one of those periods in time when the punishment meted out to those who commit incest is less severe than it has been in the past.
But the revulsion felt by the average person toward those who are discovered in incest remains strong. Why is this so?
Each of us has heard tales of the dire results of inbreeding. Writers refer to the Habsburgs, and tell of villages where incest prevails and nobody is quite sane. Or the villagers are deformed, and perhaps most children die at birth. We all recall tales of gloomy castles with crazy hermits screaming in the night. These are the things we mentally connect with the word "incest".
Others before us have made similar connections. The Zulus, for instance, believed that the spirits of their ancestors would turn the offspring born of incest into demonic monsters. The Mojave Indians held to the belief that incest foretold the extinction of the tribe, like mass suicide. The Tikopians of Polynesia believed incestuous marriages would be barren, that the offspring must surely die; the ancestors would kill them, they believed, because the other ancestors would laugh.
Genetic evidence regarding birth defects directly resulting from incest is extremely complicated, and still uncertain. The theoretical genetics of consanguinity (inbreeding) can be set out clearly enough, however. Put quite simply, it is this: We are all bred from the same ancestors; if this were not so, the population of the world a thousand years ago would have had to be a thousand times what it is now in order to give us enough ancestors.
We therefore quite often marry relatives without being aware of it. The likelihood of our meeting up with a destructive recessive gene which matches our own increases in a straight line from our most distant cousin to our own brother or sister, mother or father. But it is a slight increase only.
What has a much greater effect on the genetic structure, and increases or decreases the chance of deformation or retardation accordingly, is the amount of inbreeding that has taken place among earlier generations of the family.
If cousin marriage, or incest between brother and sister, father and daughter, or any of the other variations possible has been fairly common among our ancestors, we run no great risk of having less than normal offspring by our cousin, or sister, or daughter than by anyone else.
But if we live in a society where the restrictions against incest have long been strong, as they have been in America, England and most of Europe, where even marriage between cousins is frowned upon, if not illegal, then our chances of having substandard children as the result of incestuous pregnancy will be greatly increased.
That, at least, is the theory. Current research does indeed seem to show it reflected in reality. But none of this can have been visible to our ancestors, against the background of disease and death which prevailed when we were learning our present sexual customs; thus the strong taboo against incest must have another origin than this. The origin itself may also explain the varying strength of the taboo at different times and in different places.
Man is the only animal who recognizes his own kin once they are grown. At the point in his story when we learned to do this, and the concepts of sister, mother, daughter, father and son were formed, we began to distinguish, and endogamy and exogamy began. When two things are different, you treat them differently.
Since a marriage within the family added less strength or wealth or skill than a marriage which brought a new member into the unit, it was soon seen that incest should be discouraged, if only for reasons of survival. Among most groups it was. Among other tribes and groups, those whose survival was not so dependent on the strength of the family unit, the taboo was less strong. This probably accounts for the differences in the taboo among the cultures of today.
Feeling against incest has fluctuated throughout history, and it may be that we are now entering a period when enforcement against the taboo is on the wane. It would be wrong to conclude, however, that incest will be accepted by our culture. For, while the threat of genetic complications may have been exaggerated — and the commission of incest may be more common than previously thought — society will continue to exclude any act which fails to recognize the foundation upon which society itself is built: the family unit.
And the taboo against incest will be violated by those who choose to do so, just as it has been violated throughout history — by brothers and sisters, by mothers and sons by daughters and fathers.
Bibliography
Brecher, Edward M., The Sex Researchers. New York: The New American Library, Inc., 1971.
Freeman, Lucy, The Cry for Love. New York: Simon and Schuster, 1970.
Freud, Sigmund, Three Essays on the Theory of Sexuality. Translated by James Strachey. New York:. Avon Books, 1971.
Kinsey, Alfred C., et al., Sexual Behavior in the Human Female. New York: Signet, 1971.
Sexual Freedom League, The Southern California. Region Newsletter. Los Angeles. October 15, 1968.
Smith, James R., Consenting Adults. New York: Lancer, 1971.
Young, Wayland, Eros Denied. New York: Grove Press, 1966.